Substrates for printed circuit boards are widely used, the substrates each including an insulating base film and a metal layer disposed on a surface of the base film and being used for obtaining a printed circuit board by etching the metal layer to form a conductive pattern.
There has been a demand for a substrate for a printed circuit, the substrate having high peel strength between a base film and a metal layer so that the metal layer does not separate from the base film when folding force is applied to a printed circuit board formed by using the substrate for a printed circuit board.
In view of this, a technology relating to a substrate that is formed by laminating a copper foil forming a metal layer on a surface of a polyimide base film has been proposed in which the peel strength between the base film and the metal layer is increased by adjusting a ten-point mean roughness (Rz) of a surface of the copper foil, the surface being bonded to the base film, to be in a range of 0.7 to 2.2 μm (refer to PTL 1).